Brummel
0e8cd0832f
Replaces `Rc<RefCell<Vec<Value>>>` with a new `GlobalStore` struct for accessing global variables. This provides a more structured way to manage global values and allows for future optimizations like sharing immutable RTL portions across environments. The `GlobalStore` also includes an `rtl_len` field to distinguish between RTL and user global slots, enabling debug-time checks for writes to immutable RTL slots.